Transmission spectrum selection for locomotive consist communications

ABSTRACT

A method for transmitting data between access points in a locomotive consist is disclosed. The method may include determining, at a sending access point, the number of locomotives across which a communication signal will be sent. The method may also include selecting, based on the number of determined locomotives, a first transmission spectrum from among one or more transmission spectrums. The method may further include equalizing the communication signal using the selected first transmission spectrum and sending the equalized communication signal to a receiving access point.

TECHNICAL FIELD

This disclosure relates generally to data communication in a locomotiveconsist and, more particularly, to sending data within a locomotiveconsist by using a selected transmission spectrum.

BACKGROUND

Rail transport is commonly used to convey passengers, goods, othermaterials, etc., from one location to another. To do so, two or morelocomotives form a consist to push or pull freight and/or passenger carsalong the rails. Locomotives also generally include network componentsthat communicate with each other and facilitate user interaction via oneor more wired and/or wireless networks to monitor and/or control thelocomotive.

When a plurality of locomotives are connected to each other to form aconsist, it may be desirable for the network components within onelocomotive to communicate with network components in one or more otherlocomotives. In certain circumstances, however, environmental factorsand/or characteristics of the communication lines connecting the networkcomponents may alter the channel quality of the communication lines,interfering with the proper transmission of these communications. Thus,a system is needed to compensate for the changing channel qualities whentransmitting the data.

U.S. Patent Application Publication No. 2011/0093144 (the '144 patentapplication) to Goodermuth et al. is directed to a system forcommunicating data in a locomotive consist. In particular, the '144patent application discloses transmitting data within a locomotiveconsist between two or more locomotives. The system described by the'144 patent application, however, does not account for environmentalfactors that may alter the channel quality.

The disclosed methods and systems are directed to solving one or more ofthe problems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a method fortransmitting data between access points in a locomotive consist. Themethod may include determining, at a sending access point, the number oflocomotives across which a communication signal will be sent. The methodmay also include selecting, based on the number of determinedlocomotives, a first transmission spectrum from among one or moretransmission spectrums. The method may further include equalizing thecommunication signal using the selected first transmission spectrum andsending the equalized communication signal to a receiving access point.

In another aspect, the present disclosure is directed to a system fortransmitting data between access points in a locomotive consist. Thesystem may include one or more memories for storing instructions and oneor more processors configured to execute the instructions. Uponexecuting the instructions, the processor may determine, at atransmitting access point, the number of locomotives across which acommunication signal will be sent. The processor may also select, basedon the number of determined locomotives, a first transmission spectrumfrom among a plurality of transmission spectrums. Moreover, theprocessor may further equalize the communication signal using theselected first transmission spectrum and send the equalizedcommunication signal to a receiving access point.

In yet another aspect, the present disclosure is directed to alocomotive consist. The locomotive consist may include a plurality oflocomotives, a communications network, and a plurality of access pointsdisposed within the locomotives. The plurality of access points may becommunicatively coupled to the communications network. The plurality ofaccess points may include a processor configured to determine, at atransmitting access point, the number of locomotives across which acommunication signal will be sent. The processor may further select,based on the number of determined locomotives, a first transmissionspectrum from among a plurality of transmission spectrums. Moreover, theprocessor may equalize the communication signal using the selected firsttransmission spectrum, and send the equalized communication signal to areceiving access point.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of an exemplary locomotive consistincluding an exemplary disclosed communication system;

FIG. 2 is a pictorial illustration of an exemplary communication systemthat may be included in a locomotive of the locomotive consist of FIG.1;

FIG. 3 is a pictorial illustration of an exemplary MU-Bus modem that maybe included in the communication system of FIG. 2;

FIG. 4 is a flowchart depicting an exemplary disclosed method that maybe performed by one or more components of the communication system shownin FIG. 1 to control data communication among a plurality of accesspoints;

FIG. 5 is a flowchart depicting an exemplary disclosed method that maybe performed by one or more components of the communication system shownin FIG. 1 to control data communication among a plurality of accesspoints;

FIG. 6 is a flowchart depicting an exemplary disclosed method that maybe performed by one or more components of the exemplary communicationsystem shown in FIG. 1 to control data transmission within a locomotiveconsist by reducing interference on a communication line;

FIG. 7 is a flowchart depicting a second exemplary disclosed method thatmay be performed by one or more components of the exemplarycommunication system shown in FIG. 1 to control data transmission withina locomotive consist by reducing interference on a communication line;

FIG. 8 is a flowchart depicting a second exemplary disclosed method thatmay be performed by one or more components of the exemplarycommunication system shown in FIG. 1 to process received data packets;

FIG. 9 is a flowchart depicting an exemplary disclosed method that maybe performed by one or more components of the exemplary communicationsystem shown in FIG. 1 to determine the best data transmission methodfor successfully transmitting data on a communication line;

FIG. 10 is a flowchart depicting an exemplary disclosed method that maybe performed by one or more components of the exemplary communicationsystem shown in FIG. 1 to determine a route for transmitting the data ona communication line; and

FIG. 11 is a flowchart depicting an exemplary disclosed method that maybe performed by one or more components of the exemplary communicationsystem shown in FIG. 1 to determine a transmission spectrum fortransmitting data on a communication line.

DETAILED DESCRIPTION

FIG. 1 is a simplified pictorial illustration of a locomotive consist100 including a plurality of locomotives 110, 120, and 130 that may bemechanically coupled together. While FIG. 1 shows three locomotives 110,120, and 130, locomotive consist 100 can comprise any number of two ormore locomotives. In locomotive consist 100, locomotives 110, 120, and130 may be wired together through a multi-unit-bus (MU-bus) 140. MU-bus140 may be a communication line that includes a plurality of wires toallow data to be communicated between locomotives 110, 120 and 130. Forexample, in one embodiment, MU-bus 140 may include a bus of twenty-sevenindividual wires, each capable of carrying a signal. Additionally,locomotives 110, 120, and 130 may communicate wirelessly throughwireless routers 113, 114, 123, 124, 133, and 134.

Locomotives 110, 120, and 130 may each include an access point 111, 121,and 131, respectively. Each access point 111, 121, and 131 may beconnected to a corresponding wired intra-locomotive network 112, 122,and 132. Wired intra-locomotive networks 112, 122, and 132 may be usedto communicate data to and/or receive data from sensors, actuators,and/or other network components used to control locomotives 110, 120,and 130. Access points 111, 121, and 131 may also be communicativelyconnected to each other through MU-Bus 140 and/or wireless routers 113,114, 123, 124, 133, and 134. Access points 111, 121, and 131 mayinteract with each other to control communications across multiplenetworks, according to the various embodiments described below.

FIG. 2 is a pictorial illustration of an exemplary communication system200 that may be included in locomotive 110. While FIG. 2 illustrates thedifferent components of communication system 200 with reference tolocomotive 110, those skilled in the art will appreciate thatcommunication systems with identical or similar components may also beincluded in any other locomotive in locomotive consist 100, such aslocomotives 120 and 130, for example.

Communication system 200 may include access point 111 communicativelyconnected to one or more networks such as wired intra-locomotive network112, wireless intra-consist network 240, MU-bus 140, and wirelessintra-locomotive wireless network 220. Access point 111 may communicatewith other components within locomotive 110, such as various sensors,actuators, and/or other network components used to control locomotives,via one or more of wired intra-locomotive network 112 and wirelessintra-locomotive network 220. Access point 111 may communicate withother network devices within locomotive consist 100, such as accesspoints 121 and 131 over MU-bus 140. Additionally or alternatively,access point 111 may communicate with network devices within locomotiveconsist 100 over wireless intra-consist network 240, e.g., via one ormore wireless routers, such as wireless routers 113 and 114 shown inFIG. 1. As discussed in greater detail with respect to the embodimentsbelow, access point 111 may communicate with other access points such asaccess points 121 and 131 to control various aspects of datacommunication within the locomotive.

Access point 111 may include a processor 210, a router & bridge 212, anMU-bus modem 213, input/output (I/O) ports 214 and 215, a storage 216,and a memory 217, I/O ports 214 and 215 may facilitate communicationbetween access point 111 and one or more other network devices on wiredintra-locomotive network 112, wireless intra-consist network 240, and/orwireless intra-locomotive network 220. Likewise, MU-bus modern 213 mayfacilitate communication between access point 111 and another accesspoint on MU-bus 140. The structure and operation of MU-bus modem 213 isdiscussed in greater detail below.

Router & bridge 212 may be configured to route data packets betweenprocessor 210 and I/O ports 214 and 215 or MU-bus modem 213. Forexample, when access point 111 receives data packets from I/O ports 214and/or 215 or from MU -bus modem 213, router & bridge 212 may route thedata packets to processor 210.

Processor 210 may include one or more processing devices, such asmicroprocessors and/or embedded controllers designed and/or manufacturedby one or more of Intel™, AMD™, ARM® Freescale™, Texas Instruments,etc., or any other type of processor. Storage 216 may include a volatileor non-volatile, magnetic, semiconductor, tape, optical, removable,nonremovable, or other type of computer-readable medium orcomputer-readable storage device. Storage 216 may store programs and/orother information that may be used to implement one or more of theprocesses discussed below. Memory 217 may include one or more storagedevices configured to store information used by access point 111 toperform certain functions related to disclosed embodiments.

In one embodiment, memory 217 may include one or more programs orsubprograms loaded from the storage or elsewhere that, when executed byprocessor 210, perform various procedures, operations, or processesconsistent with the disclosed embodiments. For example, the memory mayinclude one or more programs that enable access point 111 to, amongother things, select, from among the two or more access points, a firstaccess point to output a synchronization signal and output thesynchronization signal from the first access point to the remaining oneor more access points, wherein the synchronization signal may be used tosynchronize data communication among the two or more access points.

FIG. 3 is a pictorial illustration of exemplary components that may beincluded within MU-bus modem 213. As shown in FIG. 3, MU-bus modem 213may include analog front ends (AFE) 310 and 311, modem 320, and baseband340. AFE 310 is communicatively connected to MU-bus A 350, which is apair of wires from MU-bus 140 (shown in FIG. 2), to receive and/oroutput data packets from data signals communicated over MU-bus A 350.AFE 311 is communicatively connected to MU-bus B 351, which is a secondpair of wires from MU-bus 140 (shown in FIG. 2), to receive and/oroutput data packets from data signals communicated over MU-bus B 351.AFEs 310 and 311 may also be configured to condition received oroutputted data signals according to one or more embodiments discussedbelow, e.g., by applying transmission spectrums to communication signalsto account for communication channel characteristics, implementing oneor more communication methods such as redundancy and/or multiple-inputmultiple-output methods discussed below, etc. AFEs 310 and 311 arecommunicatively connected to modem 320. Modem 320 may filter the datasignal when sending and receiving the signal from AFE 310, 311 andbaseband 340. The configuration of MU-bus modem 213 shown in FIG. 3 isexemplary and other configurations may be possible. For example, inanother embodiment, MU-bus modern 213 may include a single AFEcommunicatively connected to two modems within MU-bus modem 213.

Baseband 340 may include a processor/router 341, clock 342, and I/Oports 343 and 344 for communicating with other components within accesspoint 111. Processor/router 341 may process the data signal beforerouting it to modem 320 or other components within access point 111.Additionally, clock 342 may be used by access point 111 to establish asynchronization signal with other access points when transmitting datasignals.

FIG. 4 is a flowchart illustrating an exemplary process of controllingdata communication among a plurality of access points, such as accesspoints 111, 121, and 131, in locomotive consist 100 using asynchronization signal. In the process of FIG. 4, a first access pointfrom among the plurality of access points is selected to output asynchronization signal (Step 410). The synchronization signal is asignal that the access points used to synchronize the sending andreceiving of data packets among each other. For example, thesynchronization signal may be used to synchronize data communicationbetween the first access point and a second access point. Likewise, thesynchronization signal may be used to synchronize data communicationbetween two or more access points that are separate from the firstaccess point outputting the synchronization signal. The synchronizationsignal may also enable the plurality of access points to communicateusing a frequency division multiple access (FDMA) communication scheme.In certain embodiments, the first access point may also determinebandwidth allocation for all of the access points within thecommunication network.

In certain embodiments, the first access point selected to output thesynchronization signal may be pre-designated as a default to use its ownon-board clock to create the synchronization signal. In anotherembodiment, the first access point may be selected based on the locationof the access point within locomotive consist 100. For example, thefirst access point may be an access point in a locomotive located towardthe middle of locomotive consist 100 (e.g., access point 121).

After selecting the first access point to output the synchronizationsignal (Step 410), the first access point initiates the start of a frameby outputting the synchronization signal to the remaining access points(Step 420). For example, the first access point may initiate the startof a frame by sending a beacon signal to the other access points. Thebeacon signal announces the beginning of a data communication period.The data communication period is a period during which data iscommunicated among the plurality of access points. In certainembodiments, the first access point may establish the start of a frameby using an internal clock at the first access point, such as clock 342in MU-bus modem 213, as a master clock. Alternatively, the first accesspoint may use another clock signal from a network device incommunication with the first access point as the master clock toinitiate the start of a communication frame.

Once the other access points receive the synchronization signal from thefirst access point, the receiving access points may use thesynchronization signal to synchronize all data transmissions amongaccess points within locomotive consist 100.

One or more of the access points (e.g., access points 111, 121, and 131)may monitor the synchronization signal output from the first accesspoint to determine whether it is operating properly (Step 440). Thefirst access point itself may monitor the synchronization signal and/orone or more of the receiving access points may monitor it. Referring toaccess point 111 as an example, processor 210 or processor/router 341may be configured to monitor the synchronization signal and determinewhether it is operating correctly as a master clock. In embodimentswhere one or more of the receiving access points are monitoring thesynchronization signal, the receiving access point(s) may compare thesynchronization signal to their own internal clock signal. For example,the receiving access point may compare the synchronization signal to theclock signal generated by its own clock 342 in MU-bus modem 213, or byany other clock.

Based on the monitoring step (Step 440), the access point(s) monitoringthe synchronization signal determine whether an error has occurred withthe first access point outputting the synchronization signal (Step 450).If the access point(s) monitoring the synchronization signal determinethat it has failed (Step 450, Yes), then a new access point from amongthe plurality of access points will be selected to output a failoversynchronization signal to replace the original synchronization signal(Step 460). The process may then return to Step 420, where the newaccess point initiates the start of the frame using the failoversynchronization signal. The process will then continue as describedabove.

If the access point(s) monitoring the synchronization signal determinethat it has not failed (Step 450, No), then the first access point willcontinue to output the synchronization signal and the plurality ofaccess points will continue using the synchronization signal tocommunicate data within the system (Step 470). In this case, the processwill return to Step 440 and the access point(s) will continue to monitorthe synchronization signal (Step 440). The process will then continue asdescribed above.

FIG. 5 illustrates a process of controlling data communication among aplurality of access points in a locomotive consist using an oscillatingsynchronization signal. The steps described in FIG. 5 may be performed,for example, as a part of Step 420 in the process of FIG. 4. Forexample, Step 510 in FIG. 5 may be performed after the first accesspoint is selected to output a synchronization signal in Step 410 of FIG.4. At Step 510, the first access point generates an oscillatingsynchronization signal. The oscillating synchronization signal mayfunction as a clock signal for communicating data among a plurality ofaccess points. In certain embodiments, the oscillating synchronizationsignal may oscillate at a specific frequency, such as 60 Hz, forexample.

After generating the oscillating synchronization signal (Step 510), thefirst access point may multiplex the oscillating synchronization signalover a communication line that is communicatively coupled to theplurality of access points (Step 530). For example, the first accesspoint may multiplex the oscillating synchronization signal over one ormore wires included in MU-bus 140. By multiplexing the oscillatingsynchronization signal over the MU-bus, the first access point mayimpress a modulated carrier signal on the communication line. Thismodulated carrier signal allows for different frequency bands to be usedon the communication line. Once the frequency bands are established,data communications between locomotives may be synchronized by using theestablished frequencies. The access point may also send data to otheraccess points (Step 540). For example, the access point sends the dataamong the plurality of access points by using the clock signalestablished by the oscillating synchronization signal to allocate thedata transmissions,

FIG. 6 illustrates a process for controlling data transmission within alocomotive consist by reducing the effect that interference on acommunication line has on the data transmission. In the process of FIG.6, a sending access point (e.g., access point 111) sends data to areceiving access point (e.g., access point 131) through a first pair ofwires and a second pair of wires (Step 610). The first and second pairof wires communicatively connect the sending access point to thereceiving access point. For example, the first and second pair of wiresmay be included in MU-bus 140. When sending the data transmission, thesending access point may divide the data packets included in the datatransmission such that a first subset of the data packets are sent overthe first pair of wires and a second subset of data packets are sentover the second pair of wires, for example using a multiple-inputmultiple-output (MIMO) communication technique.

The sending and/or receiving access point may also monitor an amount ofinterference generated by the first pair of wires on the second pair ofwires when sending the data transmission from the sending access pointto the receiving access point (Step 620). For example, the interferencemay include crosstalk between the first and second pair of wires.Additionally, the access point may monitor the effect the monitoredinterference has on the data transmission. The sending and/or receivingaccess point may also monitor an amount of interference generated by thesecond set of wires on the first set of wires (Step 630). For example,the access point may monitor the crosstalk between the second and firstset of wires as well as the effect the crosstalk has on the datatransmission.

Based on the monitored interference levels determined in Steps 620 and630, the sending access point may modify data packets in subsequent datatransmissions to compensate for the level of interference between thewires and thus eliminate any potential detrimental effects that theinterference may have on the data transmission (Step 640). This may beachieved using several possible techniques such as, but not limited to,spatial multiplexing, Alamouti encoding, eigen-beamforming, etc. Forexample, before sending a subsequent data transmission, the sendingaccess point may divide data packets included in the subsequent datatransmission into a first subset of data packets to be sent on the firstpair of wires and a second subset of data packets to be sent on thesecond pair of wires, similar to the process discussed above with regardto Step 610. Then, the sending access point may modify the first subsetof the data packets based on the interference detected in Step 620 inorder to compensate for the amount of interference generated by thefirst pair of wires on the second pair of wires. Likewise, the sendingaccess point may modify the second subset of the data packets based onthe interference detected in Step 630 in order to compensate for theamount of interference generated by the second pair of wires on thefirst pair of wires. The sending access point may modify the first andsecond subset of data packets using a bit loading technique and/oranother packet modification technique. In certain embodiments, AFE 310or AFE 311 may modify the packets in the manner described above.

After the sending access point modifies the data packets to compensatefor the interference (Step 640), it may send the modified signals overthe respective wires of MU-bus 140 to the receiving access point (Step650). Upon receiving the modified signals from the sending access point,the receiving access point may organize the subsets of data packetsaccording to the MIMO scheme being implemented in order to reconstructthe message being sent over MU-bus 140.

In certain embodiments discussed above with regard to FIG. 6, the firstpair of wires and the second pair of wires may include four separatewires. That is, the first pair of wires may include a first wire and asecond wire, and the second pair of wires may include a third wire and afourth wire that are different than the first wire and the second wire.In other embodiments, however, the first pair of wires and the secondpair of wires may share a common wire, such that there are only threewires between the two pairs of wires.

The exemplary process illustrated in FIG. 7 may be used for controllingdata transmission within a locomotive consist by reducing interferenceon the communication line when the first pair of wires and the secondpair of wires share a common third wire. For example, the first pair ofwires may include a first wire and the common third wire, while thesecond pair of wires may include a second wire and the common thirdwire. The sending access point may perform Step 710 of the process ofFIG. 7 in a similar way to that described above with respect to Step 610of FIG. 6, except that in Step 710 sending access point may send thedata through the three wires that make up the first and second pair ofwires, e.g., using a MIMO communication scheme.

The sending and/or receiving access point may also monitor an amount ofinterference generated by the first wire and the common third wire onthe second wire when sending the data transmission from the secondaccess point to the receiving access point (Step 720). For example, theinterference may include crosstalk between the wires. The sending and/orreceiving access point may also monitor an amount of interferencegenerated by the second wire and common third wire on the first wire(Step 730). For example, the access point may monitor the crosstalkbetween the wires.

Based on the monitored interference levels determined in Steps 720 and730, the sending access point may encode data packets in subsequent datatransmissions to combine the signals carrying the data transmissionssuch that any potential detrimental effects of interference between thewires may be reduced (Step 740). Thus, similar to the description abovewith regard to Step 640 in FIG. 6, before sending a subsequent datatransmission, the sending access point may divide data packets includedin the subsequent data transmission into a first subset of data packetsto be sent on the first pair of wires and a second subset of datapackets to be sent on the second pair of wires. Then, in Step 740, thesending access point may encode the data to be sent along the threewires included in the first and second pairs of wires using an encodingscheme that eliminates any potential detrimental effects that theinterference may have on the data transmission. In certain embodimentsAFE 310 and/or AFE 311 may be configured to encode the data in themanner described above.

After encoding the data packets, the sending access point sends the datapackets to the receiving access point, which receives, combines anddecodes the data according to the encoding scheme employed at thesending access point (Step 750). In various embodiments, the decodingmay be performed by processor 210, processor/router 341, AFE 310, and/orAFE 311.

FIGS. 6 and 7 discussed above describe communication methods by whichaccess points 111, 121, and 131 within locomotive consist 100 maycommunicate with each other using MIMO and/or MIMO-related communicationtechniques, e.g., by dividing data packets representing a datacommunication into subsets and sending the different subsets acrosswires of MU-bus 140, and also describe how the access points may modifyand/or encode data packets to reduce interference between the wires.Access points 111, 121, and 131 may also communicate using othercommunication methods. For example, in certain embodiments, the sendingaccess point may send redundant data packets across multiple wires. Inthese embodiments, the sending access point may receive a communicationto be sent to the receiving access point. The sending access point maysend a first set of data packets representing the communication along afirst set of wires and may also send a second set of data packetsrepresenting the same communication along a second set of wires. Incertain embodiments, this type of redundant communication may be used,for example, if a channel between the sending and receiving accesspoints has a low signal-to-noise ratio (SNR), is experiencing anundesired amount of cross talk and/or packet loss, etc.

FIG. 8 is a flowchart of an exemplary process that may be performed bythe receiving access point (e.g., access point 131) when receiving datacommunicated according to the redundant communication method discussedabove. For example, the receiving access point may receive a first setof data packets representing a communication on a first pair of wires ofMU-bus 140 (Step 910), and may also receive a second set of data packetsrepresenting the same communication on a second pair of wires of MU-bus140 (Step 920). The receiving access point may receive the sets of datapackets in MU bus Modem 213 and may route the data to processor 210through AFE 310, Baseband 340, and router & bridge 212, for example.

Moreover, while the data packets sent by the sending access point mayhave been identical when they were sent, different channelcharacteristics, such as SNR, interference, etc., may cause the receiveddata packets to differ by the time they reach the receiving accesspoint. Thus, the receiving access point may process the first set ofdata packets and the second set of data packets to create a resultantset of data packets representing the communication (Step 930). Forexample, receiving access point may add together corresponding bits ofthe first set of data packets and the second set of data packets tocreate the resultant set of data packets. If the receiving access pointadds together corresponding bits of the data packets, then the receivingaccess point may determine the value of each bit within the resultantset of data packets by comparing the sum of the corresponding bits to athreshold value. In certain embodiments, this threshold value may be 1,although the receiving access point may vary the threshold based onexternal factors such as system packet loss and throughput. Adding thebits of the data packets together reduce the effects of packet loss onthe wires over which the communications are sent. In another embodiment,the receiving access point may select one of the first set of datapackets or the second set of data packets based on a determined amountof packet loss or other characteristic associated with each of the firstset of data packets and the second set of data packets. Thus, in thisembodiment, the receiving access point may use the data transmitted overone of the pairs of lines and discard the data transmitted over theother pair of lines.

After creating the resultant set of data packets, the receiving accesspoint may generate a communication related to operating the locomotivebased on the communication represented by the resultant set of datapackets (Step 940). For example, the communication may include a commandto control one or more components of locomotive 130, such as one or moresensors or actuators, for example. This way, access points withinlocomotive consist 100 can successfully communicate to facilitate thecontrol of locomotives 110, 120, and 130 within locomotive consist 100even when communication channels between the locomotives exhibit highlevels of interference. Alternatively or additionally, the communicationmay include a local area network communication, a video and/or audiotransmission or another communication function.

FIG. 9 illustrates a process for determining which communication methodto use for transmitting data between access points over a communicationline such as MU-bus 140. For example, as described below, the process ofFIG. 9 may include monitoring at least one of the first pair of wiresand one of the second pair of wires for interference and selectivelydetermining a communication method to be used between the sending accesspoint and the receiving access point based on the monitoredinterference. Monitoring the interference may include, for example,determining values representative of the SNR and/or crosstalk associatedwith the wires.

In the process of FIG. 9, the sending and/or receiving access pointmonitors crosstalk and SNR on the wires in the communication line suchas MU-bus 140 (Step 1010). Alternatively, the access point monitoringthe crosstalk and SNR may be any other access point within thelocomotive consist 100.

The monitoring access point may also determine if the SNR exceeds athreshold value (Step 1020). The threshold value may be set to apredetermined value in order to optimize data transmission. If the SNRdoes not exceed the threshold value (Step 1020, Yes), then the data willbe transmitted using the redundant communication method described withregard to FIG. 8. For example, the receiving access point may generate arequest for the sending access point to send a subsequent communicationusing the redundant communication method of FIG. 8 (Step 1040). Theprocess may then return to Step 1010 where the channels are againmonitored to determine the best communication method for subsequentcommunications.

If the SNR exceeds the threshold value (Step 1020, Yes), then themonitoring access point may determine if the signal-to-crosstalk ratioassociated with one or more of the wires exceeds a signal-to-crosstalkratio threshold value (Step 1030). The signal-to-crosstalk thresholdvalue may also be a predetermined value selected to optimize datatransmission. If the monitored signal-crosstalk does not exceed thesignal-to-crosstalk threshold value (Step 1030, No), then subsequentdata transmissions may be sent between the sending and receiving accesspoints using a MIMO communication method that includes a crosstalk orinterference compensation scheme (Step 1050), such as one of the methodsdescribe above with regard to FIGS. 6 and 7. For example, the receivingaccess point may generate a request for the sending access point to senda subsequent communication using one of the methods described above withregard to FIGS. 6 and 7. Alternatively, the MIMO communication methodmay be implemented by a plurality of single input/single output (SISO)devices that may be combined to provide MIMO functionality. For example,the access point may multiplex data packets over two pairs of wireswithout further modification. Then, a receiving access point may furtherprocess the data packets to reduce and/or cancel any crosstalk.

If at Step 1030, the monitored signal-to-crosstalk does exceed thesignal-to-crosstalk threshold (Step 1030, Yes), then the access pointwill transmit and receive data using a default communication method(Step 1060). For example, the receiving access point may generate arequest for the sending access point to send a subsequent communicationusing a default communication method. In certain embodiments, thedefault mechanism may include MIMO without crosstalk compensation. Inother embodiments, the default mechanism may include sending datapackets along a single pair of wires without any modification.

FIG. 10 illustrates a process for determining a route for transmittingthe data between access points on a communication line such as MU-bus140. In the process of FIG. 10, a first access point (e.g., access point111) monitors at least one characteristic of a data transmission betweenaccess point 111 and a third access point (e.g., access point 131) (Step1110). As shown in FIG. 1, a second access point (e.g., access point121) may be physically disposed between access point 111 and accesspoint 131 on the communication line. Additionally, a fourth access point(not shown in FIG. 1) may be disposed between access point 111 andaccess point 121 or between access point 121 and access point 131. Themonitored transmission characteristics being monitored by access point111 may include packet loss and throughput. While access point 111 isbeing used as an example, any other access point on MU-bus 140 maymonitor the characteristics of data transmissions.

Based on the monitored transmission characteristics in Step 1110, thefirst access point may determine whether to route the data transmissionthrough the second access point disposed between the first and secondaccess point (Step 1120). The access point may then route the datatransmission based on the determination made in Step 1120 (Step 1130).

For example, access point 111 may determine that the monitored packetloss and/or throughput exceeds a threshold, and, in response, maydetermine to route the data transmission from access point 111 to accesspoint 131 through access point 121. Based on this determination, accesspoint 111 will send the data transmission to access point 121. Uponreceiving the data transmission from access point 111, access point 121may send the data transmission immediately to access point 131.Alternatively, access point 121 may wait to transmit the data to accesspoint 131 until a communication line is available to send the data. If atransmission line is not immediately available, access point 121 maystore the data transmission in a buffer or memory (e.g., memory 217).Once a communication line is available, access point 121 may send thedata transmission to access point 131. While this data transmissionrouting may result in a certain amount of latency between the datatransmission from access point 111 to access point 121 and the datatransmission from access point 121 to access point 131, it may alsoresult in decreased packet loss when compared to a data transmissionthat is routed directly from access point 111 to access point 121without being routed through access point 121. The decreased packet lossmay ensure higher data transfer reliability and faster overall datatransmission. For example, by selectively routing the data transmissionthrough access point 121, only a single data transmission attempt may beneeded. On the other hand, routing directly from access point 111 toaccess point 131 may result in so much packet loss that two or more datatransmission attempts may be required before the data is successfullytransmitted from access point 111 to access point 131.

On the other hand, if the monitored data transmission's packet lossand/or throughput is within an acceptable level, then access point 111may route the data transmission from access point 111 directly to accesspoint 131. In this case, access point 111 may send the data packetdirectly to access point 131 without sending it to access point 121. Incircumstances where the packet loss and/or throughput is within anacceptable level, direct routing may result in a faster datatransmission from access point 111 to access point 131, because the datatransmission is not delayed by access point 121.

The disclosed system may also determine how to route these transmissionsby monitoring and comparing the characteristics of two or more datatransmissions between different access points. For example, one or moreaccess points may monitor and compare the characteristics of a datatransmission from access point 111 to access point 121 and then toaccess point 131 with the characteristics of a data transmissiondirectly from access point 111 to access point 131. Based on thiscomparison, the one or more access points may make a determination onthe future routing of data transmissions. For example, access point 111may determine that the net packet loss associated with the datatransmission routed through access point 121 is less than the net packetloss associated with the data transmission routed directly from accesspoint 111 to access point 131. Responsive to this determination, accesspoint 111 may route future data transmissions to access point 131through access point 121 to reduce packet loss. Those skilled in the artwill appreciate that access point 111 may make similar routing decisionsbased on other data transmission characteristics, such as throughput.For example, access point 111 may determine that the throughputassociated with the data transmission routed through access point 121 isgreater than the throughput associated with the data transmission routeddirectly from access point 111 to access point 131. Responsive to thisdetermination, access point 111 may route future data transmissions toaccess point 131 through access point 121 to increase throughput.Moreover, access point 111 may also make these routing decisions basedon optimizing a combination of data transmission characteristics, e.g.,using moving averages, weighted moving averages, etc.

While the examples described above with reference to FIG. 10 haveinvolved three access points, those skilled in the art will appreciatethat the principles can be applied to locomotive consists having anynumber of access points. For example, as discussed above, a fourthaccess point, while not shown in FIG. 1, may be disposed between accesspoint 111 and access point 121 or between access point 121 and accesspoint 131, e.g., in an additional locomotive within locomotive consist100 (also not shown). In this example, access point 111 may determine,based on monitored characteristics of one or more data transmissions,whether to route the data transmission through the fourth access point,in addition to or instead of routing the data transmission throughaccess point 121. In certain circumstances, such as where datatransmissions between access point 111 and access point 131 exhibitunsatisfactory levels of packet loss, access point 111 may route a datatransmission through both access point 121 and the fourth access pointin order to reach access point 131.

FIG. 11 illustrates a process for determining a transmission spectrumfor transmitting a communication carrying data over a communication linesuch as MU-bus 140. In the process of FIG. 11, a first access point(e.g., access point 111) determines the number of locomotives acrosswhich the communication signal will be sent (Step 1210). For example, asshown in FIG. 1, the access point 111 may determine that a communicationsignal being sent to a second access point (e.g., access point 131), maybe sent across three locomotives (e.g., locomotives 110, 120, and 130).

Based on the determined number of locomotives, access point 111 mayselect a first transmission spectrum (Step 1220). For example, accesspoint 111 may include, e.g., in memory 217 or elsewhere, one or morelookup tables that correlate different numbers of locomotives each witha first transmission spectrum. The transmission spectrum may define apre-equalization of a waveform or may alter a bandwidth over which thecommunication signal is transmitted. Access point 111 may equalize thecommunication signal using the selected transmission spectrum (Step1230). For example, the transmission spectrum may be a waveform thatequalizes a communication signal by altering the signal's gain peak.Alternatively, the transmission spectrum may alter the bandwidth of thecommunication signal by either widening or narrowing the bandwidth. Incertain embodiments, the transmission spectrum may change the spectraldensity to redistribute power over the bandwidth. Once access point 111has equalized the communication signal, it may send the equalized signalto access point 131 (Step 1240).

Access point 111 may also monitor characteristics of the communicationline over which the signal was sent (Step 1250). For example, accesspoint 111 may monitor the communication line to ensure that thecommunication signal is properly transmitted. Additionally, access point111 may monitor the communication line for other characteristics thatmay impact the quality of the data transmission, such as the SNR, packeterror rate, and received signal levels on the communication line.

Based on the monitored characteristic, access point 111 may select asubsequent transmission spectrum for subsequent communication signalstransmitted along the same path (e.g., to the same receiving accesspoint) (Step 1260). In certain embodiments, the lookup table stored ataccess point 111 may correlate both the number of locomotives and amonitored characteristic, such as SNR, with different transmissionspectra. Thus, based on the number of locomotives determined in Step1220 and the characteristic monitored at Step 1250, access point 111 maydetermine, with reference to the lookup table, the subsequenttransmission spectra to be used for a subsequent communication signal.Additionally, access point 111 may dynamically generate a newtransmission spectrum based on the monitored characteristics. Forexample, instead of selecting a predetermined transmission spectrum fromthe lookup table, access point 111 may generate a new transmissionspectrum that may include a plurality of sub-carriers within anorthogonal frequency-division multiplexing (OFDM) signal that arecustomized based on the monitored characteristics of the channel. Aftercreating the new transmission spectrum, access point 111 may store it,e.g., in storage 216 or memory 217, to be used for subsequenttransmissions. In certain embodiments, access point 111 may store thedynamically created transmission spectrum in the lookup table. Once thesubsequent transmission is selected (or created), access point 111 maysend the communication signal to access point 131 based on thesubsequent transmission spectrum (Step 1270). After sending thecommunication signal, access point 111 may continue to monitor thecharacteristic of the communication line over which the signal has beensent (Step 1250). By continuing to monitor the communication line,access point 111 may continue to adjust the data signal to account forany new environmental factors that may change over time. This way,access point 111 may ensure that data transmissions are successfullyreceived by access point 131 by adjusting the communication signal toaccount for any changes in the environment surrounding locomotiveconsist 100.

INDUSTRIAL APPLICABILITY

Methods and systems consistent with features related to the disclosedembodiments enable more reliable data transmissions between a pluralityof locomotives within a locomotive consist, by using a specifiedtransmission spectrum to equalize a communication signal and compensatefor potential degradation in the data transmission. The methods andsystems may also monitor the data transmissions within the consist andadjust the transmission spectrum in order to respond to environmentalfactors that may change over time. Thus, methods and systems consistentwith disclosed embodiments may not only reduce degradation, but may alsooptimize data transmissions by constantly monitoring and adapting tochanging environmental factors.

Moreover, while several embodiments have been described herein, thoseskilled in the art will appreciate that one or more disclosedembodiments may be combined with one or more other disclosed embodiment.For example, in addition to using a specified transmission spectrum, thesystem may also selectively change the data transmission method, e.g.,summing identical data packets on a pair of wires, in order to improvedata transmission performance. Still further, any combination of theembodiments discussed above may be combined in any manner.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed locomotiveconsist system. Other embodiments will be apparent to those skilled inthe art from consideration of the specification and practice of thedisclosed locomotive consist system. It is intended that thespecification and examples be considered as exemplary only, with a truescope being indicated by the following claims and their equivalents.

What is claimed is:
 1. A method for transmitting data between accesspoints in a locomotive consist, the method comprising: determining, at asending access point, the number of locomotives across which acommunication signal will be sent; selecting, based on the number ofdetermined locomotives, a first transmission spectrum from among aplurality of transmission spectrums; equalizing the communication signalusing the selected first transmission spectrum; sending the equalizedcommunication signal to a receiving access point; and monitoring acharacteristic of a communication line over which the equalizedcommunication signal is transmitted, wherein the monitoredcharacteristic includes an operation as a master clock synchronized withone or more other clocks operating in the consist.
 2. The method ofclaim 1, further including: selecting, from the plurality oftransmission spectrums, a second transmission spectrum based on themonitored characteristic.
 3. The method of claim 2, further including:equalizing a second communication signal using the selected secondtransmission spectrum; and sending the second communication signal tothe receiving access point.
 4. The method of claim 2, wherein themonitored characteristic includes a signal-to-noise ratio of thecommunication line, a signal level of the communication signal, or apacket error rate.
 5. The method of claim 1, wherein the transmissionspectrum defines a pre-equalization of a waveform.
 6. The method ofclaim 1, wherein the transmission spectrum alters a bandwidth over whichthe communication signal is transmitted.
 7. The method of claim 1,further comprising: dynamically generating a new transmission spectrumbased on the monitored characteristic.
 8. The method of claim 7, whereindynamically generating the new transmission spectrum includesselectively modifying a plurality of sub-carriers within an orthogonalfrequency-division multiplexing (OFDM) signal.
 9. The method of claim 7,further comprising storing the new transmission spectrum in a memoryalong with the plurality of transmission spectrums.
 10. A system fortransmitting data between access points in a locomotive consist,comprising: one or more memories storing instructions; and one or moreprocessors configured to execute the instructions to: determine, at asending access point, the number of locomotives across which acommunication signal will be sent; select, based on the number ofdetermined locomotives, a first transmission spectrum from among aplurality of transmission spectrums; equalize the communication signalusing the selected first transmission spectrum; send the equalizedcommunication signal to a receiving access Point; and monitor acharacteristic of a communication line over which the equalizedcommunication signal is transmitted, wherein the monitoredcharacteristic includes an operation as a master clock synchronized withone or more other clocks operating in the consist.
 11. The system ofclaim 10, wherein the one or more processors are further configured toselect, from the plurality of transmission spectrums, a secondtransmission spectrum based on the monitored characteristic.
 12. Thesystem of claim 11, wherein the one or more processors are furtherconfigured to equalize a second communication signal using the selectedsecond transmission spectrum and send the second communication signal tothe receiving access point.
 13. The system of claim 11, wherein themonitored characteristic includes a signal-to-noise ratio of thecommunication line, a signal level of the communication signal, or apacket error rate.
 14. The system of claim 10, wherein the transmissionspectrum defines a pre-equalization of a waveform.
 15. The system ofclaim 10, wherein the transmission spectrum alters a bandwidth overwhich the communication signal is transmitted.
 16. The system of claim10, wherein the processor dynamically generates a new transmissionspectrum based on the monitored characteristic.
 17. The system of claim16, wherein the one or more processors are further configured todynamically generate the new transmission spectrum by selectivelymodifying a plurality of sub-carriers within an orthogonalfrequency-division multiplexing (OFDM) signal.
 18. The system of claim16, wherein the one or more memories are further configured to store thenew transmission spectrum in a memory along with the plurality oftransmission spectrums.
 19. A locomotive consist comprising: a pluralityof locomotives; a communications network; a plurality of access pointsdisposed within locomotives of the locomotive consist andcommunicatively coupled to the communications network; and a processorconfigured to determine, at a sending access point, the number oflocomotives across which a communication signal will be sent, select,based on the number of determined locomotives, a first transmissionspectrum from among a plurality of transmission spectrums, equalize thecommunication signal using the selected first transmission spectrum,send the equalized communication signal to a receiving access point, andmonitor a characteristic of a communication line over which theequalized communication signal is transmitted, wherein the monitoredcharacteristic includes an operation as a master clock synchronized withone or more other clocks operating in the consist.
 20. The locomotiveconsist of claim 19, wherein the processor dynamically generates a newtransmission spectrum based on the monitored characteristic.